Dual wall exhaust manifold and method of making same

ABSTRACT

The present invention provides an improved dual-wall exhaust manifold assembly. The assembly has inner shells welded together and welded to an inlet flange. Outer shells are inserted into a counterbore of the inlet flange. An outlet flange is slid over the inner shell. The inner shell and the outer shell are inserted into the counterbore of the outlet flange. The outer shells are welded together and to the outlet and inlet flanges. The inlet counterbore and the outlet flange counterbore separate the inner and outer shells.

RELATED APPLICATIONS

This non-provisional application claims the benefit of U.S. Provisional Patent Application No. 60/756,238, entitled “DUAL WALL EXHAUST MANIFOLD,” filed Jan. 3, 2005, which is hereby incorporated by reference in its entirety.

FIELD OF ART

The present invention relates generally to exhaust manifolds, and more specifically, to dual-wall exhaust manifolds for use with internal combustion engines.

BACKGROUND OF THE INVENTION

Many modern high performance engines generate extremely hot gas emissions. As these emissions are expelled from the engine and pass through the exhaust manifold, the hot emissions heat the exhaust manifold or pipes to increasingly high temperatures. Such high temperatures cause the temperature of the tubes to elevate resulting in discoloration of the tubes. As such, some component designs utilize a dual wall construction that utilizes an air gap between the inner and outer tubes. Known dual wall manifolds utilize spacers and stub tubes to properly space the inner and outer tubes. The air gap insulates the outer tube from the inner tube. As a result, the inner tube is insulated from significant heat transfer to the outer tube. Therefore, discoloration and excessive heating are minimized. However, use of stub tubes, spacers and the related labor associated with these components is costly.

In order to manufacture the components of the manifold in a cost and labor efficient manner, manufacturers balance many factors including weld placement, weld types, component numbers, thermal expansion of components and the like. Each of these components is vital in manufacturing cost effective dual-wall components that perform and act properly under working conditions.

For example, allowing for thermal expansion tolerances is required for a properly manufactured and designed manifold assembly. Specifically, the inner tubes and other components are heated to higher temperatures than the outer tubes. Therefore, allowing for thermal expansion of the inner components is essential in a properly functioning dual-wall manifold assembly.

Furthermore, manufacturing costs of a manifold assembly can be significant, and a continual need in the industry is to reduce these manufacturing costs. Reducing the number of components of the manifold assembly can significantly reduce manufacturing and labor costs. In addition to reducing costs, the industry continues to seek any improvement in strength and durability of the assembly. Placement and type of the weld, for example, can be important in terms of manufacturing costs as well as overall strength and durability of the manifold assembly.

Therefore, there is a need in the art to provide a dual-wall exhaust manifold that can overcome at least several of the above disadvantages and achieve at lease some of the above advances desirable in the art.

SUMMARY OF INVENTION

A dual wall exhaust manifold assembly is provided. The manifold has an outer shell and an inner shell spaced apart to allow for an air gap between the shells. To ease in manufacture and assembly, the inlet flange and the outlet flange have counterbores. The counterbore of the outlet flange aids in spacing the inner shell and the outer shell. The inner shell is connected to the outlet flange with a slip fit joint. The counterbore of the outlet flange provides an area to weld the outer shell to the outlet flange. The counterbore of the inlet flange allows space for welding the inner shell to the inlet flange. Advantageously, the manifold assembly of the present invention eliminates components typically required for manufacture of a dual wall exhaust manifold, such as stub tubes and spacers.

DESCRIPTION OF THE DRAWINGS

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:

FIG. 1 illustrates inner shell joints of a dual-wall exhaust manifold assembly in an embodiment of the present invention.

FIG. 2 illustrates outer shell joints of a dual-wall exhaust manifold assembly in an embodiment of the present invention.

FIG. 3 illustrates a cross-sectional view of a welded connection between an inlet flange and an inner shell of a dual-wall manifold assembly in an embodiment of the present invention.

FIGS. 4 and 5 illustrates an underside view of a dual-wall exhaust manifold assembly in an embodiment of the present invention.

FIG. 6 illustrates an outer shell and an inner shell connected to an outlet flange of a dual-wall exhaust manifold in an embodiment of the present invention.

FIG. 7 illustrates an outer shell and an inner shell connected to an inlet flange of a dual-wall exhaust manifold in an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Although the preferred embodiment of the invention has been illustrated in the accompanying drawings and described in the subsequent detailed description, it is to be understood that the invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims as appended hereafter.

Referring to the drawings, a dual-walled exhaust manifold 10 having a body or log 11 is provided. The body 11 includes an outer shell 12 and an inner shell 14 connected to an outlet flange 16 and an inlet flange 18. The body 9 of the manifold 10 is in fluid communication with each of several runners 11 a-11 d, shown in the drawings as four in number. The illustrated manifold 10 can, for example, have any number of runners for any number of cylinders of an engine. For example, the manifold 10 can be used in a V-8 engine where the manifold 10 may be duplicated on the opposite side of the engine. The manifold assembly 10 is attachable to an engine block and the outlet (or exhaust) flange 16. Exhaust from a vehicle engine, for example, flows from the engine through passageways into the inlet flange 18 and in the runners 11 a-11 d. The engine exhaust is expelled from the manifold 10 through the outlet flange 16.

The outer shell 12 and the inner shell 14 may be formed from two or more components. Preferably, the outer shell 12 and the inner shell 14 are formed from two portions joined along a centerline of the shells 12, 14. It is also anticipated that each of the shells 12, 14 may be integrally formed. In a preferred embodiment, the outer shell 12 substantially surrounds and/or encloses the inner shell 14. The outer shell 12 may have several channels 13 corresponding in number and shape to the runners 11 a-11 d of the inner shell 14. The outer shell 12 and the inner shell 14 are positioned so that an air gap is formed between the shells 12, 14 as illustrated in FIG. 3.

The inner shell 14 may have a first portion 14 a and a second portion 14 b that are welded together, as shown in FIG. 1. In an embodiment, joints 15 of the portions 14 a, 14 b of the inner shell 14 are welded together. In a preferred embodiment, the joints 15 are welded to provide increased strength and durability. In a most preferred embodiment, the joint 15 are welded multiple times and have strength greater than typical welds. In one such embodiment illustrated in FIG. 1, the joints 15 are welded in five areas—three lip areas 17 a and two overlap areas 17 b—to increase the strength of attachment of the inner shells 14.

As shown in FIG. 2, the outer shell 12 may have a first side 12 a and a second side 12 b that are welded together. The sides 12 a, 12 b are positioned to form overlap joints, preferably two overlap joints 19 that are welded together. By overlapping the sides 12 a, 12 b of the outer shell 12, the strength and durability of the outer shell 12 is increased.

The inner shell 14 is inserted into the inlet flange 18 and welded as shown in FIG. 7. FIG. 3 illustrates areas of weld between the inner shell 14 and the inlet flange 18. In an embodiment, the inner shell 14 is welded along the outside of the inner shell 14. In a preferred embodiment, there are four welding areas 40 between the inner shell 14 and the inlet flange 18. The inner shell 14 and inlet flange 18 can then be cleaned (tumbled).

The inlet flange 18 has a counterbore 20 formed therein as shown in FIG. 7. The counterbore 20 provides a surface within the inlet flange 18 for mating engagement with the outer shell 12 and the inner shell 14. The counterbore 20 has a diameter substantially similar to the diameter of the outer shell 12. In an embodiment, the shells 12, 14 are positioned within the counterbore 20 such that there is minimal restriction in fluid flow from the inlet flange 18 into the inner shell 14. In a preferred embodiment, the counterbore 20 has a tolerance or space allowing for welding of the inner shells 14 to the inlet flange 18. In such an embodiment, the weld of the inner shells 14 to the inlet flange 18 may be welded multiple times, most preferably, four times (e.g. along the four welding areas 17). The outer shell 12 may be inserted into the counterbore 20 and welded to the inlet flange 18 as shown in FIG. 7.

The outer shell 12 is welded to the outlet flange 16 as shown in FIG. 6. In an embodiment, the outlet flange 16 is slipped or otherwise positioned onto the outer shell 12 and the inner shell 14. A counterbore 22 in the outlet flange 16 is sized to correspond to the size of the outer shell 12. The counterbore 22 provides a surface within the flange 16 for receiving the inner shell 14 and the outer shell 12. The shells 12, 14 are positioned within the counterbore 22 such that there is minimal restriction in fluid flow from the inner shell 14 through the outlet flange 16. Preferably, the diameter of the counterbore 22 is substantially similar to the diameter of the outer shell 12. The counterbore 22 may have a slightly larger diameter to accommodate and/or to provide space for welding the outer shell 12 to the outlet flange 16.

In an embodiment, the inner shell 14 is sized for a slip fit joint connection 23 to the outlet flange 16. The slip fit joint connection 23 allows for thermal expansion of the inner shell 14. Preferably, the inner shell 14 is secured to the outlet flange 16 without welding. In such an embodiment, the outer shell 12 may be welded to the outlet flange 16 and the weld continued into weld of the portions 14 a, 14 b of the inner shell 14.

The outer shells 12 are welded together and to the inlet flange 18 and outlet flange 16. The present invention does not require stub tubes as utilized in the prior art. Further, the current design is stronger than previous dual-wall exhaust components without additional welding. Because the inner and outer shells 14, 12 are separated by inlet and outlet flange counterbores 20, 22, no spacers are required. Welding the outer shell 12 to the inlet flange 18 and outlet flange 16 is stronger than prior art designs.

The outer shell 12 and the inner shell 14 are separated and/or spaced apart from each other a controlled amount such that air space or gap is formed between the shells 12, 14. The air gap serves to insulate heat from the inner shell 14. Specifically, the air can insulate the inner shell 14 from conducting or otherwise transferring heat to the outer shell 12. The amount of space between the shells 12, 14 may be predetermined based upon the specifications of the engine or components of the manifold assembly 10. The counterbores 20, 22 are formed in the flanges 16, 18 to correspond to the predetermined amount of space required between the shells 12, 14.

As described, the manifold design reduces the number of components utilized in the prior art designs, specifically reducing stub tubes and spacers. The construction allows for thermal growth of inner components and improves the strength and durability of the component. Further, the manufacture is simplified due to few component parts and a less complex construction. 

1. A dual wall exhaust manifold comprising: an inner shell having a plurality of runners for transporting exhaust gases of an engine, each of the runners having a passageway for transporting the exhaust gases from an inlet to an outlet of the inner shell; an outer shell substantially enclosing the inner shell, the outer shell spaced apart from the inner shell; an outlet flange connected to the outlet of the runners, the outlet flange having a bore formed therethrough; and a counterbore formed in the outlet flange for spacing apart the inner shell and the outer shell, wherein the outer shell is welded to the outlet flange.
 2. The dual wall exhaust manifold of claim 1 further comprising: an inlet flange welded to the inlet of one of the runners, wherein the inner shell and the outer shell are welded to the inlet flange.
 3. The dual wall exhaust manifold of claim 2 further comprising: a counterbore formed in the inlet flange, the counterbore positioning the outer shell apart from the inner shell.
 4. The dual wall exhaust manifold of claim 1 wherein the inner shell is slip fit into the outlet flange, the slit fit allowing for thermal expansion of the inner shell.
 5. The dual wall exhaust manifold of claim 1 wherein the counterbore of the outlet flange provides a space for welding the outer shell to the outlet flange.
 6. The dual wall exhaust manifold of claim 1 wherein the inner shell has a first portion and a second portion welded together along overlap areas.
 7. The dual wall exhaust manifold of claim 1 wherein the outer shell has a first side and a second side welded together, the first side and the second side welded at an overlap joint.
 8. A dual wall exhaust manifold comprising: an inner shell having a plurality of runners formed therein, each runner receiving exhaust gases at an inlet and expelling the gases at an outlet; an outer shell substantially enclosing the inner shell, the outer shell having a plurality of channels for enclosing the runners; an inlet flange attached to the inlet of one of the runners, the inlet flange having a bore and a counterbore, the counterbore sized to receive the inner shell and the outer shell wherein the counterbore of the inlet flange positions the outer shell apart from the inner shell to form an air gap between the inner shell and the outer shell.
 9. The dual wall exhaust manifold of claim 8 wherein the inner shell and the outer shell are welded to the inlet flange.
 10. The dual wall exhaust manifold of claim 9 wherein the counterbore of the inlet flange has a space for welding the inner shell to the inlet flange.
 11. The dual wall exhaust manifold of claim 8 wherein the counterbore of the inlet flange has a diameter substantially equal to a diameter of the runner.
 12. The dual wall exhaust manifold of claim 11 wherein the inner shell is welded to the inlet flange without inhibiting fluid flow from the inner shell through the inlet flange.
 13. The dual wall exhaust manifold of claim 8 further comprising: an outlet flange attached to the outlet of the runners, the outlet flange having a bore formed therethrough.
 14. The dual wall exhaust manifold of claim 13 wherein the outlet flange has a counterbore spacing the outer shell apart from the inner shell.
 15. The dual wall exhaust manifold of claim 14 wherein the outlet flange has a slip fit joint to secure the inner shell, the slip fit joint allowing for thermal expansion of the inner shell.
 16. A dual wall exhaust manifold comprising: an inner shell having a first portion and a second portion welded together, the inner shell having a plurality of runners for transporting exhaust gases of an engine, each of the runners transporting the gases from an inlet to an outlet; an outer shell having a front side and a rear side welded together, the outer shell substantially surrounding the inner shell; an inlet flange positioned on the inlet of the runners, wherein the inner shell and the outer shell are welded to the inlet flange; and an outlet flange positioned on the outlet of the runners, the outlet flange having a slip fit joint for connecting to the inner shell, wherein the outer shell is welded to the outlet flange.
 17. The dual wall exhaust manifold of claim 16 wherein the first portion and the second portion of the inner shell are welded along an overlap area.
 18. The dual wall exhaust manifold of claim 17 wherein the inner shell is welded along lip areas located between the runners of the inner shell.
 19. The dual wall exhaust manifold of claim 16 wherein the front side and the rear side of the outer shell are welded along an overlap joint.
 20. The dual wall exhaust manifold of claim 16 wherein the weld between the outer shell and the outlet flange extends into the weld of the first portion and the second portion of the inner shell. 